The invention relates to alumina, silica or silica-alumina containing catalysts, their manufacture and their use, particularly for the hydrotreatment of hydrocarbon oils, mainly those derived from oil or oil fractions or from coal hydrogenation products.
The catalysts mostly used in the field of hydrorefining of oil or oil fractions comprise a carrier such as alumina, silica or silica-alumina and at least one metal or compound of a metal from groups V and/or VI and/or VIII, in particular vanadium, molybdenum, tungsten, nickel, cobalt and/or one or more noble metals. The alumina (or silica) may be pure or contain additional components, depending on the considered use, for example alkali or alkaline-earth metals, rare earth metals, silica (or alumina), magnesia, thoria, halogen, in a proportion up to 10%, sometimes 30% or more. For sake of simplification, any of these materials will be called "carrier material" in the following disclosure.
These catalysts may have various shapes such as powder particles, spherical or ovoid balls, extrudates of circular or polylobal section, or pellets. For use as fixed, moving or expanded bed, the extrudates are usually of a diameter from 0.8 to 3 mm.
Extrudates may be manufactured in a manner well known in the art by passing a moist paste of carrier material, optionally with additional porogenous agents well known in the art, through calibrated orifices.
The extrudates are then "matured", i.e. kept in humid atmosphere, at moderate temperature, for example at about 60.degree. to about 100.degree. C., then dried at about 100.degree. to 200.degree. C. and calcined at about 300.degree. to 1000.degree. C. (activation treatment):
The calcined extrudates can then be used as catalyst carrier: they are impregnated with a solution of catalytic elements or their precursors. However, the catalytic elements or their precursors can be introduced into the moist paste of carrier material and the resultant mixture can be subjected to the above-mentioned operations of shaping, drying and calcination at about 300.degree. to 1000.degree. C.
For various applications, when the extrudates contain alumina, it may be advantageous to subject the extrudates, after calcination, to a subsequent treatment with water or steam, called "autoclaving", at a temperature from about 80.degree. C. to about 300.degree. C. for about 5 minutes to 48 hours, preferably from 1 to 6 hours.
The autoclaving aqueous medium preferably comprises at least one acid able to dissolve at least a portion of the alumina conglomerates, or the mixture of such an acid with at least one compound supplying an anion able to combine with aluminum ions, for example a mixture of nitric acid and acetic or formic acid.
The extrudates from the autoclaving step are then dried and activated by heating at a temperature of about 300.degree. to 1000.degree. C.
The above-mentioned autoclaving technique is described, for example, in the French Pat. No. 2,496,631.
When using autoclaving, the catalytic materials or their precursors may be introduced either before the extrusion of the carrier material or after the calcination performed after said extrusion, as already indicated above, or preferably after the autoclaving treatment and the subsequent thermal activation. In this latter case, after introduction of the catalytic elements, the resultant product is dried and calcined at 300.degree.-1000.degree. C. and/or reduced, according to known techniques.
The resultant extrudates usually have a surface from 50 to 350 m.sup.2 /g, preferably from 100 to 250 m.sup.2 /g, and a total pore volume from 0.4 to 1.5 cc/g, preferably from 0.8 to 1.2 cc/g.
The autoclaving treatment and/or the thermal treatments modify the structure of alumina, silica and/or silica-alumina and the characteristics thereof, particularly the specific surface and the porosity, this modification being useful for certain catalytic uses, particularly hydrorefining. More particularly, the autoclaving treatment, mainly when performed in acid medium, confers to the alumina-containing hydrorefining catalysts of the above-described type an exceptional resistance to poisoning by metals and/or asphaltenes deposition.
The catalysts of the invention are particularly useful in the domain of hydrotreatment (hydrodesulfuration, hydrodenitrogenation, hydrocracking, hydrometallation) of hydrocarbon oils containing metals and asphaltenes, for example crude oil, straight-run or vacuum distillation residues, deasphalted residues, bituminous sands or shales extracts, coal liquefiates.
These catalysts also have numerous other applications, for example in reforming of gasoline and naphtha, hydrogenation of unsaturated compounds and treatment of exhaust gases from internal combustion engines.